In his book "Unweaving the Rainbow" Richard Dawkins goes into this a little. He quoted the same time period, 62 million years, but also another shorter period of 26 million years for smaller scale extinctions.

One theory he offered is that our sun is part of a binary system with an orbit of 26 million years, with the unseen 2nd star causing orbital disturbances in swarms of comets and asteroids leading to increased metorite impacts with Earth.

I read somewhere that our solar system passes through the galactic plane in our revolution every 20 some million years.